Tissue Targeting

Optimal delivery of the radioconjugate depends on several factors—pharmacokinetics of the conjugate and the biological parameters of the tissue. The physical half-life of the isotope should be longer than the time needed for targeting the tissue/tumor aiming for a maximal tissue-to-background ratio. Usually, for cancers with a large number of circulating tumor cells such as leukemia, cancer cells can be easily targeted within a short interval after administration. The size of the conjugate (e.g., antibody) is also an important factor that determines the pharmacokinetics. Similarly, the morphology of the tumor including the level of antigen expression and interstitial pressure can affect delivery of the radioconjugate. These factors result in either suboptimal delivery or poor target-to-background ratio. These are not limiting factors in treating benign or malignant pathology in cavitary lesions where the radioconjugate is either directly instilled into the resection cavity or after-loaded into an indwelling balloon catheter. However, there should be no or minimal leakage into the blood pool and the conjugate/carrier needs to be inert.

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